1. Field of the Invention
The present invention relates generally to vacuum waste tanks. More particularly, the present invention relates to a polar cap for vacuum waste tank of an aircraft waste system that carries a separator, an inlet, a diverter, a sensor and/or a rinse nozzle.
2. Related Art
As typically know to most travelers, flushing an aircraft toilet results in the waste fluids and solids being “sucked” from the toilet bowl into a tank via a drain pipe. This fundamental process provides a system that is relatively simple, low in weight, and low in odor in comparison to other systems, like a re-circulating toilet used in older aircraft. The principles of this system are based on the pressure differential between the cabin pressure inside the aircraft and the lower air pressure outside of the aircraft at flight altitude. When a patron flushes a toilet, a valve opens to the outside air creating a decrease in pressure or “vacuum” on the sewage waste system in comparison to the cabin pressure. This vacuum pulls the waste fluids and solids from the toilet bowl, through a drain line, and into a holding tank. When the aircraft is on the ground or at lower flight altitudes where this differential of pressures is less than optimal, a vacuum blower is used to boost the differential pressure to the necessary level for the waste system to function correctly.
The fundamental parts of this system include a toilet bowl, a drain line to the holding tank, the holding (waste) tank, and vacuum lines connecting the waste tank to the vacuum blower and the atmosphere outside the aircraft. The waste tank is a simple vacuum vessel used to retain the waste fluids and solids flushed down the toilet until the time the aircraft has landed and tank can be drained. The tank can include sensors, waste inlets and diverts, rinse system, drain, and air-water separator.
The sensors detect the level of the waste inside the tank determining how full the tank is. The sensors are mounted at a certain height along the inner face of the tank wall. They function by contacting the waste fluids and solids and creating an electronic signal. When the tank is full, the sensors will shut down power to the restrooms connected to it.
The waste inlets and diverts connect the drain line from the toilets to the waste tank. The inlets support the waste system in such a way that the vacuum pressure in the tank draws the waste matter from the toilet, through the drain pipe, through the inlets, and into the tank. The ends of the inlets have a profile that fastens or clamps to the drain pipes in such a way that the connection can be easily removed. This interface provides a water-tight seal with the use of an o-ring or gasket to prevent leakage of fluids and solid waste. The diverts work in conjunction with the inlets of the tank and are aligned with the inlets on the inside of the tank. The diverts work to direct the flow of the waste matter that comes into the tank away from the sensors and reduce the splash of matter as it enters the tank. The intent of the diverts is to reduce coating the sensor faces with a buildup of waste fluids and solids that can result in the sensors giving a false reading of a full tank and minimize the amount of fluids and solids impacting the air-water separator.
Rinse systems are installed into the waste tank in which clean water can be sprayed through the rinse system to clean out the inside of the waste tank during servicing. One of the primary aspects of the rinse system is to remove the liquid and solid waste buildup from the face of the sensors in order to ensure the sensors are providing accurate readings of the waste level in the tank.
The drain allows the waste material to be easily removed from the vacuum waste tank while the aircraft is being serviced. Service personnel open a valve in the bottom of the aircraft allowing the waste matter to drain out of the waste tank, through a drain line, and out of the aircraft.
The air-water separator, which typically sits at the top of the waste tank, connects the tank to the vacuum lines that run to the vacuum blower and the exterior of the aircraft. The separator filters out liquid and solid particulates entrained in the air flow which is generated by vacuum from the external pressure differential or the vacuum blower. The separator filters out liquid and solid particulates though the use of baffles and a filtering mesh which is typically assembled in a replaceable filter canister. Depending on the design of the separator, the filter canister can sit fully inside the tank, partially inside the tank, or external of the tank.
The current waste tank systems have several shortcomings in their designs. First, the sensors, rinse systems, and inlets/diverts require penetrations through the tank wall. This reduces the strength and structural integrity of the tank. Second, the mounting fittings that attach these items to the tank require well trained technicians, specialized equipment, and a large amount of time to repair and replace the fittings. Third, the penetrations in the tank and the incorporation of the fittings provide potential leak paths for fluids and solid waste to escape the vacuum waste system which becomes a biohazard. Lastly, the fittings limit the flexibility of the tank size and shape. A new tank design with a slight variation in size or shape would require new fittings and thus expensive molding tools.